Formation of heavy element rich giant planets by giant impacts

Abstract

AbstractWe have performed the smoothed particle hydrodynamic (SPH) simulations of collisions between two gas giant planets. Changes in masses of the ice/rock core and the H/He envelope due to the collisions are investigated. The main aim of this study is to constrain the origin and probability of a class of extrasolar hot Jupiters that have much larger cores and/or higher core/envelope mass ratios than those predicted by theories of accretion of gas giant planets. A typical example is HD 149026b. Theoretical models of the interior of HD 149026b (Sato et al. 2005; Fortney et al. 2006; Ikoma et al. 2006) predict that the planet contains a huge core of 50-80 Earth masses relative to the total mass of 110 Earth masses. Our SPH simulations demonstrate that such a gas giant is produced by a collision with an impact velocity of typically more than 2.5 times escape velocity and an impact angle of typically less than 10 degrees, which results in an enormous loss of the envelope gas and complete accretion of both cores.